玻璃态PS焓松弛β参数的热历史依赖性  

Thermal History Dependence of Kohlrausch Parameter β in Enthalpy Relaxation of Glassy Polystyrene

作　　者：李丽霞[1] 赵冬梅[1] 范留彬[1] 刘国栋[1] 

机构地区：[1]河北工业大学高分子科学与工程研究所,天津300130

出　　处：《河北大学学报（自然科学版）》2011年第6期617-622,共6页Journal of Hebei University(Natural Science Edition)

基　　金：国家自然科学青年基金资助项目(20804013);教育部功能高分子材料重点实验室开放基金

摘　　要：用TNM模型研究了PS的焓松弛,将模型参数Δh,x和lnA作为材料常数,假定β参数随热处理条件变化,提出了新的参数优化方法:由极限假想温度T′f求取Δh;由T′f和峰值温度Tmax求取x和lnA,不同热处理条件下的β值由对归一化比热CpN数据进行拟合得到.T′f,Tmax和CpN的理论计算值都与实验结果十分接近,得到的参数具有规律性,β随热处理条件变化,当降温速率从100K/min降到0.1K/min时,β从0.498降到0.341,在363.15K下恒温老化,随老化时间延长β呈现极大值0.504,从结构松弛的角度对上述结果进行了解释.Structural relaxation and physical aging of glassy polymers are important topics in polymer science.The relaxation was characterized by nonexponentiality and nonlinearity.The enthalpy relaxation of PS was restudied by adapting TNM model in this paper.Δh,x and lnA were assumed to be material constants while β to be a thermal history dependent parameter.Based on this assumption,a new optimizing method was proposed.Δh was obtained by fitting limiting temperature Tf′,x and lnA were obtained by fitting Tf′ and Tmax,while the individual β was obtained by fitting the normalized heat capacities CNp.The fitting results of both Tf′,Tmax and CNp were perfect well.The best-fit Δh,x and lnA were obtained to be 114 kK,0.247 and-300.72 s-1,respectively.β was found to be thermal history dependent.It decreased from 0.498 to 0.341 when the cooling rate deceased from 100 to 0.1 K/min while showed a maximum of 0.504 with the increasing annealing time at 363.15 K.The observed result was tentatively interpreted by conceiving that β changes along the thermal treatment and the obtained value maybe an apparent one.The apparent β may be determined by Tf′ and Tg of the sample with different thermal history as well as the temperature range it experienced.

关 键 词：PS β参数 玻璃化转变 焓松弛 热历史 

分 类 号：O631.5[理学—高分子化学]